As it has been revealed that production of active oxygen species in the living body and accompanying production of peroxylipid have a variety of adverse influences on the living body through membrane disorder or enzyme disorder, various attempts have been made to apply lipid peroxidation inhibitory agents to medicaments. Currently, as lipid peroxidation inhibitory agents used in the pharmaceutical field, derivatives of natural antioxidants such as vitamin C, vitamin E and P-carotene, etc. and phenol derivatives are mainly known (authored by Kenji Fukuzawa, Nippon Rinsho vol. 46, pp 2269–2276, 1988 and Sies, H., Stahl, W., Sundquist, A. R., Ann. N. Acad. Sci., vol. 669, 7–20, 1992). However, these have insufficient activities and have side effects and, therefore, they are not necessarily satisfactory practically.
On the other hand, WO97/32871 describes, as a furo[3,2-f]indole derivative, compounds represented by the formula: wherein R1 denotes a hydrocarbon group, an optionally substituted amino group or an optionally substituted heterocyclic group, R2 denotes hydrogen atom or an optionally substituted hydrocarbon group, R3 denotes hydrogen atom, an optionally substituted hydrocarbon group or an optionally substituted heterocyclic group, X denotes CHR4, NR4, O or S(R4 denotes hydrogen atom or an optionally substituted hydrocarbon group), Y denotes C, CH or N (provided that, when X denotes CH2, Y is C or CH),                 denotes a single bond or a double bond,        
A ring denotes an optionally substituted 5- to 7-membered oxygen atom-containing heterocyclic ring, B ring denotes an optionally substituted benzene ring, and n denotes an integer of 1 to 4, which have the excellent melatonin receptor affinity, or salts thereof, more particularly, compounds: and the like.
WO93/22317 describes quinoline derivatives represented by the formula: wherein A ring represents furan ring, dihydrofuran ring or dioxolane ring,                R1 denotes hydroxy group, carboxyl group, an alkoxycarbony group, a carbamoyl group, an alkenyl group, formyl group, cyano group, an optionally substituted alkyl group, or —C(═N—R10)—R1 (wherein R9 denotes amino group or an alkyl group, R10 denotes hydrogen atom or hydroxy group),        R2s are the same or different and denote hydrogen atom, an optionally substituted alkyl group, an alkenyl group, an acyl group or hydroxy group,        R3 and R4 are the same or different and denote hydrogen atom, a halogen atom, an optionally substituted alkyl group, an optionally substituted amino group, an alkoxy group, an alkylthio group, carboxyl group, an acyl group, a carbamoyl group, cyano group or nitro group,        R5, R6, R7 and R8 are the same or different and denote hydrogen atom or an alkyl group,        - - - means that a double bond formed by R5 and R8 may exist, and pharmaceutically acceptable salts which are useful as a cardiac disease treating agent, more particularly, compounds:         
JP-A 54-163598 describes 2,3-dihydro or 2,3,10,11-tetrahydro-7-oxo-1H, 7H-furo or thieno[2,3-g]pyrid[3,2,1-i,j]quinoline-6-carboxylic acid derivatives or salts thereof which have antibacterial activity, as well as compounds: wherein R3 denotes a lower alkyl group, and other symbols are as defined above, as a synthetic intermediate therefor.
Lipid peroxidation inhibitory agents (antioxidants), which have lipid peroxidation inhibitory activity based on excellent antioxidant activity and are excellent in pharmacokinetics, can be expected to have excellent activity for preventing or treating central nervous diseases and disorders (for example, ischemic central nervous disorders (e.g., cerebral infarct, cerebral bleeding, cerebral edema etc.), central nervous system injury (for example, cranial trauma, head injury, spinal injury, whiplash injury etc.), neurodegenerative diseases (for example, Alzheimer's disease, Parkinson's disease, Huntington's chorea, amyotrophic lateral sclerosis etc.), vascular dementia (for example, multi-infarct dementia, Binswanger's disease etc.), manic-depressive psychosis, depressive disease, schizophrenia, chronic pain, trigeminal neuralgia, migraine etc.), circulatory diseases or disorders (for example, ischemic cardiac failure (for example, cardiac infarct, angina etc.), arterial sclerosis, arterial restenosis after PTCA (percutaneous transluminal coronary angioplasty), inferior urinary tract diseases or disorders (for example, dysuria, urinary incontinence) etc.), diabetic neurosis and the like. However, currently, since sufficiently satisfactory inhibitory agents have not been found, it has been desired to develop compounds having excellent lipid peroxidation inhibitory activity, which are sufficiently satisfactory medicaments.